JPH0756630Y2 - Power protector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a power supply protection device connected to a power supply device or the like of a welding machine.

(B) Conventional technology and its drawbacks In power supply devices such as welding machines, recently, reduction in size and weight,
A switching type power supply device that switches an input power supply voltage and outputs the same to a load has been used for higher performance. However, since a transistor is generally used as the switching element, the maximum rated current is low unlike the SCR used in the conventional power supply device. In addition, since switching type power supply devices generally have a smoothing capacitor built-in, the voltage supplied to the switching circuit does not drop even if an instantaneous power failure occurs, but the voltage supplied to the switching control circuit drops in a short time. Therefore, there is a possibility that the operation of the control circuit becomes unstable and a transistor is insufficiently driven or an erroneous switching pulse is generated, and in this case, there is a disadvantage that the transistor is destroyed.

(C) Purpose of the invention The purpose of the invention is to solve the above-mentioned inconvenience, automatically stop the operation of the switching circuit of the power supply device when the power supply is interrupted, and prevent the switching circuit from being destroyed. Provide a power supply protection device that stabilizes the operation of the power supply circuit when power is restored by not starting the switching circuit immediately after restoration, but starting the switching circuit after the control circuit etc. becomes stable. To do.

(D) Configuration and Effect of the Invention The invention includes a switching circuit that normally switches an input power supply voltage to supply power to a load, and a switching control circuit that stops a switching operation when a switching operation stop control signal is active. A power supply protection device connected to a power supply device having: a first capacitor for charging an input power supply voltage through a separate path; and a second capacitor having a smaller capacity than the first capacitor.
Capacitor, a constant voltage circuit driven by the charging voltage of the first capacitor, a switch element that outputs a switching operation stop signal to the power supply device in an on or off state, an output voltage of the constant voltage circuit, and The voltage of the difference of the charging voltage of the second capacitor is divided to give a bias voltage to the switch element, and the first and second capacitors are charged with a stable constant voltage, and the second capacitor is discharged. A resistance voltage dividing circuit for switching the ON / OFF state of the switching element depending on the input power supply voltage drop, which is in a state, and a discharge circuit for rapidly discharging the charging voltage of the second capacitor when the input power supply voltage drops. Characterize.

According to the present invention by configuring as described above,
In a normal state where the input power source is not a power failure, the first and second capacitors are charged with a stable constant voltage. As a result, the resistance voltage dividing circuit outputs the divided voltage value of the difference between the output voltage of the constant voltage circuit driven by the charging voltage of the first capacitor and the charging voltage of the second capacitor. When the input power source voltage drops, the charging voltage of the second capacitor is rapidly discharged by the discharging circuit, and the voltage division value of the resistance voltage dividing circuit changes. As a result, the on / off state of the switch element is switched, and the switching operation stop control signal is output to the power supply device.

When a power failure occurs in this way, the switching operation stop control signal is immediately formed, so that the operation of the switching control circuit is stopped by this signal, and when the power is restored, the second capacitor is completely charged before the switching operation is completed. Since the stop control signal is not generated, it is possible to prevent transistor destruction of the switching circuit at the moment of momentary power failure, and to stably start up the power supply circuit when the power is restored.

(E) Embodiment FIG. 1 is a circuit diagram of a power protection device according to an embodiment of the present invention. The input power supply voltage V1 is input to the primary side of the transformer T, the secondary side output is rectified by the rectifier circuit D, and is supplied to the first capacitor C1 and the second capacitor C2 through another path. The charging voltage of the capacitor C1 is supplied to the constant voltage circuit K1, and the constant voltage output is supplied to the transistor Q1 via the resistor R1.
Be guided to the base of. The transistor Q1 constitutes the switching operation stop circuit of the present invention. In addition, the constant voltage circuit K1
Is led to the collector of transistor Q1 via resistor R3.

The charging voltage of the second capacitor C2 is supplied to the constant voltage circuit K2 and also to the base of the transistor Q1 via the resistor R2. At this time, the polarity of the voltage supplied to the base of the transistor Q1 is negative. Further, a discharge circuit including a diode D1 and the resistor R2 is connected to the capacitor C2.

The resistors R1 and R2 act as a resistor voltage divider circuit that divides the voltage difference between the output voltage of the constant voltage circuit K1 and the charging voltage of the second capacitor C2, and its output is supplied to the base of the transistor Q1.

The capacitance of the second capacitor C2 is the same as that of the first capacitor.
It is set to be much smaller than the capacity of C1. When the capacitor C2 is not supplied with power, the charging voltage of the capacitor C2 is instantaneously discharged through the discharging circuit including the diode D1 and the resistor R2. The charging voltage of the capacitor C1 supplies a constant voltage to the constant voltage circuit K1 for a certain period of time even if the power supply to the capacitor C1 is stopped. As a result, when a power failure occurs, the bias supplied from the capacitor C2 to the transistor Q1 instantly becomes 0, but the bias voltage supplied from the constant voltage circuit K1 is held for a fixed time. Resistors R1 and R2 are sized to put transistor Q1 in the reverse bias state when capacitors C1 and C2 have a stable and constant charging voltage, that is, in the normal state where the power supply voltage is supplied. There is. Therefore, when the power is supplied, the transistor Q1 is in the off state, and when the power failure occurs, it immediately shifts to the on state. On the other hand, when the power is restored, charging of the capacitor C2 is started, but the transistor Q1 is turned into the reverse bias state and turned off only when the charging voltage of C2 becomes sufficiently large. For this reason, the transistor Q1 is switched from the on state to the off state after a lapse of a certain time after the power is restored.

When the transistor Q1 is in the ON state, the switching operation stop control signal A becomes low level, that is, the active state, and the switching control circuit shown in FIG. 2 described later stops the operation of the switching circuit. On the contrary, when the transistor Q1 is off and the signal A is at high level, the switching circuit operates.

In this embodiment, as shown in the figure, a capacitor C2 is connected in parallel with a capacitor C3, a series circuit of a Zener diode ZD and a relay CR1 is connected in parallel with this capacitor C3, and a collector base of a transistor Q1 is further connected. The series circuit of the resistor R4 and the contact XC of the relay CR1 is connected. Contact XC is a contact that opens when relay CR1 is on and closes when relay CR1 is off. The capacitor C3 is for supplying a stable voltage to the Zener diode ZD, the relay CR1 and the constant voltage circuit K2.

With the above configuration, when the power supply voltage is the rated voltage, the relay CR1 is turned on, so that the contact XC is opened and the transistor Q1 is kept off. However, when the power supply voltage becomes extremely unstable and the voltage across the capacitor C3 drops below a certain voltage (the Zener voltage of the Zener diode ZD), the relay CR1 turns off and the contact XC closes. Then, the bias voltage supplied from the constant voltage circuit K1 to the base of the transistor Q1 sharply rises, and the reverse bias state is changed to the positive bias state. At this time, the transistor Q1 shifts from the off state to the on state, and the switching operation stop control signal A becomes active. The Zener diode ZD has a Zener voltage that turns off the relay CR1 when the power supply voltage drops to a voltage at which the switching control circuit becomes unstable. Therefore, when the power supply voltage immediately before the switching control circuit enters the unstable operation region is reached, the signal A can be generated to stop the switching operation.
As a result, in the present embodiment, the switching operation can be stopped automatically at the time of power failure and also when the power supply voltage becomes unstable and drops to a certain level.

FIG. 2 is a block diagram of the power protection device shown in FIG. 1 and the power supply device to which the power protection device is connected. In FIG. 2, the switching circuit 18 is a circuit for switching the input power supply voltage to supply power to the load 17, and the switching control circuit 1 is a circuit for performing switching control of the switching circuit 18. The power supply device 20 is configured by both circuits. It
The power protection device 19 gives a switching operation stop control signal A to the switching control circuit 1. In the figure, 14 is a transformer, and 11 and 12 are switching transistors for connecting and disconnecting the current flowing through the primary winding of the transformer 14. The rectifying / smoothing circuit 13 rectifies and smoothes the input power source and supplies a DC voltage to the primary side of the transformer 14. The drive circuits 9 and 10 drive the switching transistors 11 and 12. The rectifying / smoothing circuit 15 rectifies and smoothes the secondary side output of the transformer 14 and supplies a DC voltage to the load 17. Reference numeral 16 is a voltage detection circuit for detecting the load supply voltage.

The switching control circuit 1 includes an oscillation circuit 2, a triangular wave generation circuit 3, a reference voltage generation circuit 4, an error amplification circuit 5, a comparison circuit 6, an AND gate 7 and a frequency division circuit 8. The error amplifying circuit 5 amplifies the difference voltage of the output voltage of the voltage detecting circuit 16 with respect to the reference voltage 4, and the comparator circuit 6 compares the output voltage of the error amplifying circuit 5 as a threshold value to compare the triangular wave to perform PWM control. Generate a square wave signal. The AND gate 7 divides the rectangular wave signal output from the comparison circuit 6 by the frequency dividing circuit 8 when the switching operation stop control signal A output from the power protection device shown in FIG. 1 is at a high level (inactive). The signals are cycled and output alternately to the drive circuits 9 and 10. When the switching operation stop control signal A is low level (active), the output of the AND gate 7 maintains low level. As a result, the switching operation of the switching transistors 11 and 12 is stopped.

As described above, in this embodiment, the capacity of the second capacitor C2 is made smaller than that of the first capacitor C1 and the charging voltage of the second capacitor C2 is rapidly discharged at the time of power failure, and the discharge Since the state is detected and the switching operation stop control signal is activated, the switching operation can be immediately stopped in the event of a power failure. When power is restored, capacitor C2
Since the switching operation stop control signal is made inactive by charging the battery sufficiently, it is possible to eliminate an unstable state at the time of starting after a momentary power failure.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power protection device according to an embodiment of the present invention. FIG. 2 is a block diagram of the power supply protection device and a power supply device to which the power supply protection device is connected. C1 ... first capacitor, C2 ... second capacitor, Q1
...... Transistor (switch element), K1 ...... Constant voltage circuit, (R1 + R2) ...... Resistance voltage divider circuit, (D1 + R2) ...... Discharge circuit

Front page continuation (72) Masahiro Aoyama Inventor Masahiro Aoyama 2-14-3 Awaji, Higashiyodogawa-ku, Osaka-shi, Sansan Electric Co., Ltd. (72) Inventor Kunio Kano 2--14-3 Awaji, Higashiyodogawa-ku, Osaka, Osaka Sansan Electric Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A power supply device having a switching circuit that normally switches an input power supply voltage to supply power to a load and a switching control circuit that stops a switching operation when a switching operation stop control signal is active. And a second capacitor having a smaller capacity than the first capacitor for charging the input power supply voltage through separate paths.
Capacitor, a constant voltage circuit driven by the charging voltage of the first capacitor, a switch element that outputs a switching operation stop signal to the power supply device in an on or off state, an output voltage of the constant voltage circuit, and The voltage of the difference of the charging voltage of the second capacitor is divided to give a bias voltage to the switch element, and the first and second capacitors are charged with a stable constant voltage, and the second capacitor is discharged. A resistance voltage dividing circuit for switching the ON / OFF state of the switching element depending on the input power supply voltage drop, which is in a state, and a discharge circuit for rapidly discharging the charging voltage of the second capacitor when the input power supply voltage drops. Characteristic power protection device.